Compound Interest Calculator
See how an investment grows with compound interest and optional regular contributions. Calculated entirely in your browser.
Enter a principal and a term in years to see results.
Year-by-year breakdown
| Year | Contributed | Interest | Balance |
|---|
How to project compound growth
- Enter the initial principal, the annual interest rate, and the number of years.
- Choose a compounding frequency: annually, semiannually, quarterly, monthly, or daily.
- To model regular saving, add a regular contribution and set its frequency (yearly, monthly, or quarterly).
- Read the final balance, total contributions, and total interest, then open the year-by-year breakdown to see the balance grow each year.
When to use it
It answers the question of what a sum becomes over time: a retirement pot, a savings goal, or a lump sum left to grow. The breakdown table splits the ending balance into the money you put in and the interest it earned, which is where compounding shows its effect over a long horizon.
It is also for comparing choices. Raise the rate or the compounding frequency and watch the final balance change, or add a monthly contribution to see how much steady saving adds on top of the starting principal. The figures assume a constant rate, so treat them as a projection, not a promise.
Frequently asked questions
How is the interest compounded?
At the frequency you choose: annually, semi-annually, quarterly, monthly, or daily. Each period the balance grows by the annual rate divided by the number of periods, and the calculation steps period by period rather than using a single closed-form formula.
How do regular contributions work?
You set a fixed amount added monthly, quarterly, or yearly. Contributions are deposited on their own schedule, after that period’s interest, and they work even when the contribution schedule differs from the compounding frequency.
What currency does the calculator use?
None in particular; it’s just numbers. Enter amounts in whatever currency you think in; results are formatted with two decimal places, without a currency symbol.
Is my financial information sent anywhere?
No. The amounts you enter never leave the page. Everything is computed in your browser, with no server involved.
Can I rely on these figures for financial decisions?
Treat them as estimates for information only, not financial advice. The model assumes a constant nominal rate and fixed contributions; real accounts differ in rate changes, fees, taxes, and timing, so verify important figures with your provider.